In the course of treating and preparing subterranean wells for production, a well packer or bridge plug is run into the well on a work string or a production tubing. The purpose of the packer or bridge plug is to provide isolation between zones of the wellbore. For example, the packer or bridge plug can be used to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer or bridge plug location. The packer or bridge plug is typically provided with anchor slips having opposed camming surfaces which cooperate with complementary opposed wedging surfaces; whereby the anchor slips are radially extendible into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces.
The packer or bridge plug also carries annular seal elements which are expandable radially into sealing engagement against the bore of the well casing. Longitudinal movement of the packer components which set the anchor slips and the sealing elements may be produced either hydraulically or mechanically.
After the packer or bridge plug has been set and sealed against the well casing bore, it should maintain sealing engagement upon removal of the hydraulic or mechanical setting force. Moreover, it is essential that the packer or bridge plug remain locked in its set and sealed configuration while withstanding hydraulic pressure applied externally or internally from the formation and or manipulation of the tubing string and service tools without unsetting the packer or bridge plug or without interrupting the seal. This is made more difficult in deep wells in which the packer or bridge plug and its components are subjected to high downhole temperatures, for example temperatures up to and exceeding 400° F., and high downhole pressures, for example, 5,000 pounds per square inch (“psi”).
One common problem with packers and bridge plugs is the need to prevent slipping in both an uphole and downhole direction. Often slip assembly used with packers and bridge plugs use angled gripping elements that prevent slippage in one direction but are subject to slippage in the opposite direction. Some packers use bi-directional slip assemblies; that is, slip assemblies with gripping elements that do not favor either the uphole or downhole direction. However, these can be difficult to set adequately in the casing and, if not adequately set, are subject to slipping under the downhole forces.